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What is Biodiversity Net Gain?
Biodiversity Net Gain (BNG) is a new legal requirement affecting most types of planning applications in England. It came into force in February 2024. In 2026 the new process is well embedded and all applications need to address BNG even if it is to certify it does not apply.
The intention of the new legislation is to ensure the biodiversity value of development sites is measurably improved as a result of development. To achieve this, the law requires most planning applications to demonstrate a minimum 10% gain for biodiversity. The 10% is calculated using a BNG Metric.
To which sites and developments does Biodiversity Net Gain apply?
The new BNG requirement has applied to major sites* since February 2024. Small sites** have been subject to BNG since the start of April 2024.
*For residential sites, this means sites that have an area of 0.5 ha or greater or where 10 or more homes are proposed. For non-residential sites, this means sites that have an area of 1 ha or greater or where additional floorspace of 1000 sqm or more is proposed.
**This means non-major sites.
Exemptions
The following sites and developments remain exempt:
- Householder developments. These are developments that affect an existing house or its grounds, including domestic extensions, domestic outbuildings and domestic enclosures (fences, gates etc.)
- Certain self-build and custom housebuilding applications. These are applications for new dwellings that are to be built by or on behalf of an individual (or collection of individuals) for occupation by that individual. The exemption only applies where:
- The development consists of no more than 9 dwellings AND
- The development site has an area of no more than 0.5 hectares AND
- All dwellings in the application are of the self-build or custom build type.
De Minimis exemptions
There is also a de minimis exemption. This means development that meets both of the following two tests is exempt from the BNG requirement:
- The development does not impact an onsite priority habitat
- The development impacts:
- Less than 25 square metres of onsite habitat that has a biodiversity value greater than zero
- Less than 5 metres in length of onsite linear habitat.
In some local areas, Councils have adopted their own Biodiversity Net Gain planning policies that apply to sites and developments that would otherwise be exempt from the legal BNG requirement. If this is the case in your area, you will be expected to comply with the local BNG policy.
Definition of key terms
- Priority habitat – these are specified habitats of principal importance to UK biodiversity. The list of priority habitats includes arable field margins, bogs, hedgerows, woodland, traditional orchards, heathland, reedbeds, meadows, rivers, ponds and more.
- Biodiversity value – biodiversity value is measured using the government’s statutory biodiversity metric tool. The metric takes into account the size, condition, strategic significance and type of on-site habitats. If a site has a biodiversity value of zero that means it has no biodiversity value at all. This would likely apply, for example, to a site covered throughout by tarmac, concrete or traditional buildings
- Linear habitat – hedgerow and watercourse habitats.
What do I need to do about Biodiversity Net Gain?
Exempt sites
If your development is exempt, you must include a statement explaining why it is exempt alongside your planning application.
Liable sites
If your development is liable for BNG, you are required by law to submit a Biodiversity Gain Plan before you commence development. You must not commence development until the plan is approved. The plan will demonstrate how the minimum 10% biodiversity gain will be achieved. The government has produced a Biodiversity Gain Plan template which is available online. Note some councils are now introducing policy requiring a larger than 10% requirement. Uttlesford is the latest to do this in March 2026.
In addition, you must submit a biodiversity metric calculation alongside your planning application (the BNG metric). This must be calculated using the government’s statutory biodiversity metric tool which is also available online (see Government Guidance). Further guidance can also be found here at RTPI guidance and Natural England guidance. The metric assessment should be completed by a competent person. Although you do not necessarily need to share your Biodiversity Gain Plan with the council at this stage, you will likely require a draft version in order to complete the metric assessment.
Our advice
Our advice is to submit your draft Biodiversity Gain Plan alongside your planning application as you may receive valuable feedback on its contents that will assist you to refine it. This will increase the chances of your finalised plan being approved the first time around.
Finally, you will need to submit a plan (drawing) that accurately shows the type and extent of all existing site habitats. This will require a site walkover.
How do I achieve a 10% gain for biodiversity?
Option 1 – onsite
The government’s expectation is that the full 10% gain will be delivered within the boundaries of the development site wherever possible. This will be achieved via the provision of new or enhanced green infrastructure. This includes things like woodlands, hedgerows, meadows, ponds and any other landscape features that provide wildlife habitats. You can extend or improve an existing habitat or create a whole new one.
The land owner will be legally responsible for both creating and maintaining the new habitat/s for a minimum period of 30 years.
If the 10% gain cannot be delivered onsite, there are two remaining options. However, you must be able to clearly justify why the net gain cannot be achieved onsite. If you are able to deliver less than the 10% gain onsite then you should do so and use the remaining options to make up the shortfall.
Option 2 – offsite
If you are unable to deliver the full 10% gain onsite, then the next best option is to deliver the gain offsite. This means creating new or enhanced habitats on land outside of the development site. This could be on adjacent land but the site can be anywhere in England. The biodiversity metric does look more favourably on offsite gains that are located close to the development site, however.
You can either make your own offsite gain on land in your ownership or you can buy offsite “units” from a land manager. There are already many companies in England offering these units for sale.
If you choose to deliver the gain on your own land, you will be legally responsible for maintaining the new habitat/s for a minimum period of 30 years. If you purchase your offsite units from a land manager, they will be legally responsible for maintaining the habitat/s over this period.
Option 3 – statutory biodiversity credits
Buying statutory credits is a last resort. It is only an option for developers who cannot achieve onsite or offsite biodiversity net gain. Developers who wish to buy statutory credits must explain why they cannot achieve the 10% gain using one or both of the preferred options outlined above.
Developers can use a combination of the 3 options but must prioritise options 1 and 2, in order. If, for example, a developer is able to achieve a 5% onsite gain and a 3% offsite gain then they should only purchase statutory credits to make up the remaining 2%.
To purchase statutory credits, you must submit an application to Natural England. Natural England aims to consider your application within 8 weeks. Any credits you purchase will be non-refundable.
Follow the link below to find out more about the application process.
Table showing delivery options in 2026
| Delivery method | Priority level | Description |
|---|---|---|
| On-site biodiversity gains | 1 – highest priority | The preferred method. Biodiversity is enhanced or created within the red line boundary of the development site through habitat retention, enhancement and new habitat creation. |
| Off-site biodiversity gains | 2 – secondary priority | Used where the full 10% gain cannot be achieved on-site. Biodiversity units are delivered on land outside the development site, either on the developer’s own land or via purchased off-site units from a registered provider. |
| Statutory biodiversity credits | 3 – last resort | Used only where on-site and off-site solutions cannot deliver the required gain. Credits are purchased from the government and are intended to be a fallback mechanism, not a preferred delivery route. |
How biodiversity units are measured in practice
Biodiversity Net Gain is measured using the government’s statutory biodiversity metric. That metric converts habitats into standardised biodiversity units by assessing the habitat’s size, type, condition and strategic significance. For newly created or enhanced habitats, the metric also takes account of delivery risk, including the difficulty of creation or enhancement, the time needed to reach target condition, and the distance from the habitat loss.
There are three separate types of biodiversity units in the metric:
| Unit type | What it measures | Typical measurement | Why it matters |
|---|---|---|---|
| Area habitat units | Habitats such as grassland, woodland, scrub, ponds and other area-based features | Usually measured by area | These units cover most habitats found on development sites. |
| Hedgerow units | Hedgerows and lines of trees | Usually measured by length | Hedgerows are assessed in their own module and are not simply folded into area habitat units. |
| Watercourse units | Rivers, streams, ditches and other qualifying watercourses | Usually measured by length | Watercourses are assessed separately because they have their own characteristics and risk factors. |
A key point is that these three unit types are not interchangeable. You cannot usually make up for the loss of area habitat units by adding more hedgerow, and you cannot offset watercourse losses by creating grassland elsewhere. The statutory metric treats each module separately, and the requirement to achieve at least 10% net gain applies to each relevant unit type.
Practical examples of pre- and post-development calculations
The examples below are illustrative only. Actual results depend on the statutory metric and the detailed habitat survey.
| Unit type | Pre-development position | Post-development position | Net result | What this means |
|---|---|---|---|---|
| Area habitat units | Existing site contains habitats worth 5.00 area units | After development and on-site habitat creation, the site provides 5.60 area units | +12.0% | This would exceed the minimum 10% BNG requirement for area habitats. |
| Hedgerow units | Existing hedgerows are worth 1.20 hedgerow units | After retaining part of the hedge and planting new native hedgerow, the site provides 1.35 hedgerow units | +12.5% | This would exceed the 10% requirement for hedgerows. |
| Watercourse units | Existing ditch or stream corridor is worth 0.80 watercourse units | After bank improvements and habitat enhancement, the site provides 0.92 watercourse units | +15.0% | This would exceed the 10% requirement for watercourses. |
A simple way to think about BNG
In simple terms, the biodiversity metric compares the site before development with the site after development, then checks whether the finished scheme delivers enough habitat value to show a measurable uplift. The metric can therefore be used to test design options early, compare different layouts, and work out whether a shortfall must be met on-site, off-site or, only as a last resort, through statutory biodiversity credits.
A more detailed worked example
Example 1: Area habitats
A site starts with rough grassland and scattered scrub assessed at 5.00 area habitat units. A first draft layout removes too much green space and leaves only 4.40 units, which would be a 12% loss. The scheme is then redesigned to include a species-rich meadow, extra tree planting and better retained habitat, increasing the post-development value to 5.60 units. That produces a 12% gain, so the area habitat requirement is met.
Example 2: Hedgerows
The site begins with boundary hedgerows worth 1.20 hedgerow units. If part of the hedge is removed for access and little replacement planting is provided, the total may fall to 0.90 units, a 25% loss. If the design instead keeps most of the existing hedge and adds a new native hedgerow, the result could rise to 1.35 units, giving a 12.5% gain.
Example 3: Watercourses
A development site includes a ditch or stream corridor worth 0.80 watercourse units. If the scheme narrows buffers and provides no ecological enhancement, the total may fall to 0.72 units, which is a 10% loss. If the design introduces improved margins, better habitat structure and suitable enhancement works, the post-development result could rise to 0.92 units, which would be a 15% gain.
Note habitat types are assessed seperately
Because area habitats, hedgerows and watercourses are assessed separately, a compliant scheme may need to show a 10% uplift in more than one category, depending on what is present on the site at baseline.
How Biodiversity Net Gain fits into wider environmental policy
Biodiversity Net Gain is not a standalone box-ticking exercise. It sits alongside the wider planning and environmental policy framework in England, which is concerned not only with replacing habitat losses, but also with protecting important sites, improving ecological connectivity and supporting long-term nature recovery. Government planning guidance explains that BNG is a measurable requirement under the statutory framework, while national planning policy also expects plans and decisions to minimise impacts on biodiversity and pursue measurable net gains.
BNG complements protected sites rather than replacing their protection
A useful way to explain BNG is that it is an additional requirement, not a substitute for existing protections. National planning policy requires plans to identify, map and safeguard local wildlife-rich habitats and wider ecological networks, including the hierarchy of internationally, nationally and locally designated sites of importance for biodiversity. The same policy framework also requires the promotion of conservation, restoration and enhancement of priority habitats, ecological networks and priority species, and the pursuit of measurable biodiversity gains. In other words, BNG sits alongside the protection of designated sites and wider biodiversity policy rather than replacing it.
Planning practice guidance also makes clear that the ordinary mitigation hierarchy still applies: first avoid harm, then mitigate it, and only as a last resort compensate for residual harm. The guidance expressly distinguishes that mitigation hierarchy from the separate biodiversity gain hierarchy used for BNG delivery. That distinction is important, because it means a development cannot simply rely on BNG to bypass proper site selection, avoidance or mitigation.
The same point is especially clear in relation to irreplaceable habitats. Official government guidance states that mandatory BNG does not change the existing strong protections and compensation requirements that already apply to those habitats in planning policy. Where irreplaceable habitat is affected, bespoke compensation may still be required, and the normal BNG calculation does not simply override that issue.
BNG helps strengthen ecological networks
BNG is also intended to do more than improve individual development sites in isolation. National planning policy says that plans should identify and safeguard wider ecological networks, including wildlife corridors, stepping stones and areas identified for habitat management, enhancement, restoration or creation. That is important because species recovery often depends on connected habitats rather than small, isolated pockets of green space.
Planning practice guidance explains that Local Nature Recovery Strategies map the places where habitat creation or improvement would be especially beneficial, including for building and strengthening local ecological networks. It also explains that local ecological networks contribute to the wider Nature Recovery Network, which the NPPF glossary describes as an expanding and increasingly connected network of wildlife-rich habitats supporting species recovery, alongside wider benefits such as carbon capture, water quality improvements, natural flood risk management and recreation.
This gives BNG a wider strategic purpose. When off-site habitat creation or enhancement is needed, Local Nature Recovery Strategies can help direct it to the right places so that gains are not scattered randomly, but instead support larger and more joined-up areas for wildlife. Government guidance states that LNRSs can play a critical role in supporting off-site gains in a way that maximises biodiversity benefits and helps create bigger, better connected areas in which wildlife can thrive.
BNG integrates with wider environmental policy goals
BNG also links to broader environmental policy objectives. Government guidance on Local Nature Recovery Strategies says they should identify proposals not only for nature recovery, but also for wider environmental goals. Planning practice guidance adds that LNRS information can help identify locations where habitat improvement would support wider environmental outcomes such as flood risk management, climate change mitigation and an improved water environment.
That means a well-designed BNG strategy can deliver multiple benefits at the same time. For example, habitat creation and enhancement can be planned to support biodiversity while also improving green infrastructure, strengthening landscape structure, storing carbon, improving water management and helping reconnect fragmented habitats. In that sense, BNG is part of a broader move in planning policy towards nature recovery, climate resilience and better environmental quality, rather than a narrow mathematical exercise.
Summary table: how BNG fits into the bigger picture
| Wider policy theme | How BNG fits in | Why this matters |
|---|---|---|
| Protected sites and habitats | BNG operates alongside existing planning policy and habitat protections; it does not replace the need to protect designated sites or properly address impacts through the planning process. | It helps explain that BNG is an additional measurable uplift, not a workaround for harm to important habitats or sites. |
| Ecological networks | BNG supports habitat restoration and creation in ways that can strengthen wildlife corridors, stepping stones and wider ecological networks. | It shows that BNG is about improving connectivity, not just counting units on one site. |
| Nature Recovery Network and LNRS | Off-site gains can be guided by Local Nature Recovery Strategies so habitat is created in places where it will have the greatest strategic benefit. | It helps link individual developments to larger-scale nature recovery. |
| Wider environmental outcomes | BNG can support objectives such as climate resilience, improved water environments and flood risk management when habitat enhancements are planned strategically. | It shows clients and councils that BNG can contribute to more than biodiversity alone. |
What Biodiversity Net Gain service does Planning Direct offer?
Planning Direct can assist you with all aspects of Biodiversity Net Gain. We are able to produce most BNG documents in-house. For larger and more complex developments, some BNG documents will be produced by one of our trusted ecology partners to ensure compliance with the legislation.
BNG only
We offer a standalone Biodiversity Net Gain service. This is suitable for site owners and developers who already have a handle on all other aspects of their planning application, e.g. planning drawings, written statements, reports and case management.
Comprehensive planning service
Planning Direct also offers a comprehensive planning application service at a competitive rate. If your application is liable for BNG, we will include it as standard. If you choose this service, we can ensure your BNG strategy is considered and incorporated from the earliest design stages. This will reduce the likelihood of delays or additional, unexpected costs further down the line.
In all cases, our BNG service includes:
- Site survey
- Completion of the statutory biodiversity metric calculation
- Creation of a Biodiversity Gain Plan.
How much control will I have?
There is no “one size fits all” approach to biodiversity and we can help you to work out which strategy is best for you. For example, if you’d like to incorporate biodiversity into the garden plan for your new home, we can assist you to select the best biodiversity features for each area, based on your unique vision, budget and maintenance capabilities. This approach will enable you to meet the biodiversity requirement whilst enhancing, at the same time, the amenity value and visual appeal of your garden.
Need to keep costs down?
On the other hand, if your primary goal is to keep costs down, we can assist you to design and deliver a cost-effective, robust and low maintenance biodiversity plan.
As with all our planning services, if you tell us your aims, we will tailor our approach to help you meet them!
If your development is affected by BNG, contact us today to find out how we can assist you. Our initial advice is always free of charge.
If you’d like to learn more about Biodiversity Net Gain, you can follow the link below to access an online copy of the government’s primary BNG guidance.
Frequently Asked Questions
What is Biodiversity Net Gain?
Biodiversity Net Gain (BNG) is a legal requirement affecting most planning applications in England. It is intended to ensure development leaves biodiversity in a measurably better state than before, usually by delivering at least a 10% gain.
Who do BNG rules effect?
All builders and developers. It potentially applies to all market development over 25 sq m.
Does Biodiversity Net Gain apply to all developments?
No. Some developments are exempt, including householder development. Certain self-build and custom build schemes may also be exempt, and there is also a de minimis exemption. In some areas, local planning policies may still require biodiversity improvements even where the national legal requirement does not apply.
Is BNG Mandatory?
No. If you are not developing or development is less than 25 sqm then it is exempt. This is known as the De Minimis exemption.
When did Biodiversity Net Gain come into force?
BNG has applied to major sites since February 2024 and to small sites since April 2024.
What do I need to submit for a BNG planning application?
If your development is liable for BNG, you will usually need a biodiversity metric calculation alongside the planning application, and a Biodiversity Gain Plan must be approved before development starts. You will also normally need a plan showing the type and extent of existing site habitats.
How is BNG delivered?
BNG can be delivered on or off site via planting and maintenance. Off site BNg credits can be bought from providers.
Can the 10% gain be achieved off-site?
Yes. The preferred approach is to deliver the gain on the development site wherever possible. If that is not possible, offsite habitat creation or enhancement can be used. Statutory biodiversity credits are intended as a last resort.
How long must biodiversity enhancements be maintained?
Habitat created or enhanced to meet BNG requirements must generally be maintained for a minimum of 30 years.
What Biodiversity Net Gain service does Planning Direct offer?
Planning Direct can assist with site survey work, completion of the statutory biodiversity metric calculation, and preparation of a Biodiversity Gain Plan. For larger or more complex developments, specialist ecology input can also be provided through trusted partners.
What legal framework is behind BNG?
Biodiversity Net Gain (“BNG”) was introduced through national legislation as part of a wider shift towards embedding environmental improvement within the planning system. The principal legal change came through the Environment Act 2021, which inserted section 90A and Schedule 7A into the Town and Country Planning Act 1990. Schedule 7A now provides the core statutory framework for BNG in England, and that framework was subsequently refined by the Levelling-up and Regeneration Act 2023 and supporting secondary legislation made in 2024.
What does this mean practically?
In practical terms, the legislation means that, subject to specified exemptions and transitional provisions, planning permissions in England are deemed to include a statutory “biodiversity gain condition”. The legal objective is that development must achieve at least a 10% increase in biodiversity value when compared with the pre-development biodiversity value of the onsite habitat. That uplift is assessed using the statutory biodiversity metric, and can be delivered through a combination of onsite habitat enhancement, registered offsite biodiversity gains and, where necessary, statutory biodiversity credits.
Pre-commencement requirements
A key part of the legal structure is that BNG is not merely an aspiration at application stage: it operates as a pre-commencement requirement. Once planning permission has been granted, development cannot lawfully begin until a Biodiversity Gain Plan has been submitted and approved by the relevant planning authority. That plan must normally include the completed metric calculation, plans showing the existing and proposed habitats, details of any offsite units or statutory credits relied upon, and arrangements for the management and monitoring of significant onsite gains. The planning authority must also consider how the Biodiversity Gain Hierarchy has been applied, with the regime prioritising avoidance and mitigation first, then onsite enhancement, then offsite gains, and finally statutory credits as a last resort.
Long Term Delivery
The legislation also secures long-term delivery rather than short-term planting or cosmetic landscaping. Where a development relies on significant onsite habitat enhancement, that enhancement must be secured by planning condition, section 106 obligation or conservation covenant and maintained for at least 30 years after completion of the development. The mandatory regime commenced for applications made on or after 12 February 2024, with small developments brought into scope from 2 April 2024. There are, however, defined exemptions, including householder development, certain de minimis impacts, some self-build and custom build schemes, biodiversity gain sites, and certain development order permissions.
Citations:
Environment Act 2021, Schedule 14.https://www.legislation.gov.uk/ukpga/2021/30/schedule/14
Town and Country Planning Act 1990, section 90A and Schedule 7A. https://www.legislation.gov.uk/ukpga/1990/8/schedule/7A
Planning Practice Guidance: Biodiversity net gain. https://www.gov.uk/guidance/biodiversity-net-gain
GOV.UK guidance: Submit a biodiversity gain plan. https://www.gov.uk/guidance/submit-a-biodiversity-gain-plan
The Biodiversity Gain Requirements (Exemptions) Regulations 2024. https://www.legislation.gov.uk/uksi/2024/47/contents/made
The Biodiversity Gain (Town and Country Planning) (Modifications and Amendments) (England) Regulations 2024. https://www.legislation.gov.uk/uksi/2024/50/pdfs/uksi_20240050_en.pdf